1. Field Of The Invention
The present invention relates generally to a railway cushioning apparatus, and particularly to a gas return type of railway cushioning apparatus.
2. Description Of The Prior Art
Railway cars often use cushioning apparatus associated with the car coupling devices located on the end of the railway cars, to absorb shocks created when railway cars are connected, and also to absorb shocks created during so-called "train action events" which occur as the train is under way. These cushioning apparatus are generally referred to as end-of-car cushioning devices.
A typical end-of-car cushioning device of the type previously manufactured by the assignee of the present invention is shown in U.S. Pat. No. 3,589,527 to Seay, et al. That device is a hydraulic cushioning device which utilizes a mechanical return spring. It will be apparent upon a comparison of the drawings of the present application to the disclosure of the Seay '527 patent that the arrangement of the housing, cylinder, cylinder end plate, piston, shaft and flapper valve of the apparatus of the present invention is somewhat similar to that of the Seay '527 patent.
It is also known in the art to utilize compressed gas in a hydraulic cushioning unit so that the compressed gas provides a return force which allows mechanical springs like those of the Seay '527 patent to be eliminated. One example of such a gas return cushioning unit is shown in U.S. Pat. No. 4,026,418 to Hawthorne.
One problem which has to be dealt with when using a gas return cushioning unit is the assembly of the cushioning unit with the railway car at the customer's facility.
If the cushioning unit is charged with compressed gas prior to shipment to the customer, then the customer must deal with the placement of a fully extended cushioning unit into the sill of the railway car. As will be appreciated by those skilled in the art, the cushioning unit is constructed to closely fit within the longitudinal dimensions of the railway car sill when fully extended.
One solution is to dimension the cushioning unit so that when it is in its fully extended position it will just fit within a railway car sill of specified standard dimensions. A problem with that approach is that inaccuracies and/or tolerances allowed during the construction of the railway car sill may cause the sill to be slightly shorter than specified. Also, tolerances are present in the construction of the cushioning units themselves. This combination of inaccuracies and/or tolerances may provide occasional situations where the fully extended cushioning unit is longer than the particular railway car sill opening into which it is to be placed. In such a situation, some means must be provided for holding the cushioning unit in a partially compressed position as it is placed within the railway car sill.
As will be appreciated by those skilled in the art, due to the size and weight of these cushioning units and the difficulty of placing them in the railway car sills, it can be a difficult and dangerous operation to hold a unit partly compressed while placing it in a car sill.
Another approach to this problem is to ship the cushioning unit to the customer in an uncharged condition. The unit is then mounted in the railway car, and subsequently compressed gas is added to the unit by the customer.
The difficulty with this approach is that it is inconvenient and undesirable for the customer to have to perform the gas charging procedure. Also, the gas charging pressure cannot be controlled by the manufacturer and this presents the possibility of improper charging which can lead to improper functioning of the cushioning unit.